This invention relates to a surface illuminant device of side-light type and a flat-panel display device using this surface illuminant device.
Flat-panel display devices such as liquid crystal display devices have been used as image display devices for television set, various computers, car navigation system and the like because of their features that they are thin and light-weighted and consume a small electric power.
For example, a liquid crystal display device of light transmission type includes a liquid crystal panel, constituted by a pair of transparent substrates and a liquid crystal layer between the substrates, and a surface illuminant device disposed on a rear surface (a surface opposite to an image display surface) of this liquid crystal panel for providing illuminant light to this liquid crystal panel.
To make this type of flat-panel display device thin and compact, it is necessary to make the surface illuminant device thin. In view of the above, the main stream of the surface illuminant devices (backlights) has been shifting from direct backlight to the side-light type back light (edge-light type surface illuminant device).
As disclosed in JP-U-63024529 (Japanese Utility Model publication, unexamined 63-24529(1988)), the edge-light type surface illuminant device includes a tubular light source, and a light guide plate formed of a thin plate or an acrylic resin or the like and having a milky white scattering pattern printed on its rear surface. One end face of the light guide plate is disposed close to the tubular light source. Accordingly, the illuminant light emitted from the tubular light source is propagated in the light guide plate and is scattered by the scattering pattern on its rear surface, so as to be emitted from liquid-crystal-panel-side rain surface of the light guide plate.
The tubular light source is arranged along one to three edges (or side-end faces) of the rectangular light guide plate and has both ends thereof respectively connected with power wirings. These two power wirings are usually arranged in one power socket, which is disposed in the vicinity of one end of the tubular light source. In this way, the tubular light source is replaceable together with this power wirings and the power socket. The two power wirings from this power socket to the tubular light source usually consists of a short wiring which is connected to one end of the tubular light source and a long wiring which is connected to the other end of the tubular light source. These wirings are called harness in general.
In case the tubular light source is disposed along two or three edges (or side-end faces) of the light guide plate, in particular, in case the tubular light source is disposed in an approximately U-shape along three edges, the long power wiring is extended or pulled around from one side to the other side of the light guide plate along the edge of the light guide plate where the tubular light source is not disposed. In this specification, the portion of the power wiring for the tubular light source, which extends along the edge region where the tubular light source is not disposed, is called a pull-around line hereinafter.
In FIG. 8 and FIG. 9, the arrangement of the pull-around line in the conventional surface illuminant device 110, 120 is schematically shown.
In FIG. 8, a pull-around line 121 which connects a tubular light source 122 and a power socket 124 is disposed in such a manner that the pull-around line 121 creeps along a aide-end face of a light guide plate 101.
In FIG. 9, the pull-around line 121 is disposed in such a manner that the pull-around line 121 creeps on a lower face of a lower-side frame 104 rear-face side frame of the surface illuminant device 120).
As shown in FIG. 8, in case the pull-around line 121 is disposed at the outside of the side-end face of the light guide plate 101, the area of non-light-emitting region on the peripheral portion of the surface illuminant device 110 is increased corresponding to such an arrangement. Accordingly, when the surface illuminant device 110 is assembled into a flat-panel display device, the width of a non-image-display region (picture-frame region) at the peripheral portion of the flat-panel display device becomes wide.
As shown in FIG. 9, in case the pull-around line 121 is disposed on the lower side of the lower-side frame, the thickness of the surface illuminant device 120 and the thickness of a flat-panel display device into which the surface illuminant device 120 is assembled become large.
In particular, with respect to portable flat-panel display devices, there has been a case that even a potential plan on new products is difficult to be adopted without achieving a further progress in making the devices compact and thin.
In view of the above drawbacks, it is an object of the present invention to provide a surface illuminant device and a flat-panel display device which can achieve a further miniaturization and thinning.
In a surface illuminant device of the present invention which includes; a tubular light source having both ends thereof respectively connected with power wirings; and a light guide plate being arranged in such a manner that side-end faces thereof are disposed close to the tubular light source and an incident light from the tubular light source through the side-end faces is propagated in the light guide plate and is emitted from an upper face of the light guide plate; wherein side-end faces or edges of whole periphery of the light guide plate consists of side-end face(s) or edge(s) at which the tubular light source is disposed closely and the other side-end facet(s) or edge (s) at which the tubular light source is not disposed; and at least one of the power wirings includes a pull-around line which extends along the other side-end face(s) or edge(s) at which the tubular light source is not disposed; further comprising a groove-like or notch-like receiving portion, which extends continuously along the side-end face(s) or edge(s) at which the light source is not disposed, is formed in the light guide plate; and the pull-around line is at least partially accommodated in the receiving portion.
Due to such a construction, the surface illuminant device can be made compact and thin. Furthermore, it gives rise substantially no increase of the manufacturing cost.
According to one preferred embodiment, the receiving portion has the sufficient depth and the width to accommodate the pull-around line.
Due to such a construction, the pull-around line can be accommodated within an original contour of the light guide plate. Moreover, the manufacturing of the device is facilitated.
According to another preferred embodiment, the pull-around line is fitted into the receiving portion.
In one particular preferred embodiment, the depth and the width of the receiving portion are set smaller than the corresponding sizes or the pull-around line so that the pull-around line is protruded downwardly thus forming a downward protrusion, and a slit which receives such a protrusion is formed in a cover which covers the lower face of the light guide plate, and the protrusion is inserted in this slit in such a manner that the protrusion hermetically seals the slit.
Due to such a construction, by reducing the depth of receiving portion, the influence given to the light guide plate by forming the receiving portion can be minimized while the increase of the size of the contour can be minimized.
According to another preferred embodiment, a light reflector member is interposed between the pull-around line and the light guide plate.
According to still another preferred embodiment, a sheath of the pull-around line is white.
Due to such a construction, even when neither a reflector sheet nor a reflector film coating is provided to the receiving portion of the light guide plate, the performance of the light guide plate is not deteriorated.